I have seen a few people use a particular file that has "u" type teeth that are wide apart. In Dr. Ashby's report on the last page (11) of the 2004 part 1 there it sits.
What's the name of that type of file?
All mine says on it is. ENGLAND
I know where you can get one if you want one. Send me a pm if you do.
Curved tooth file. They can have a tang for a handle or flexible with a hole near each end to mount to a frame to impart a curve. I believe they're generally used in auto body work.